In recent years, various kinds of onboard cameras mounted in a vehicle and shooting a driving environment in front of (or behind) the vehicle have been proposed. However, conventionally, when the onboard camera shoots a driving environment in front of the vehicle through a front windshield (front glass) during the driving in the daytime, a dashboard or the like is reflected on the front windshield, and this reflection is superimposed on an acquired image of the front or the back of the vehicle, so that the accuracy and contrast of the acquired image are degraded. As means for solving this problem, a technique for installing a polarization filter on a front face of the camera or in the vicinity thereof (outside of the field of view of the imaging lens) is known by the following Patent Documents.